Simon tip: watching the Yellowstone gate cam

Here’s a fun example of using Simon for a purpose that may not be entirely obvious.

My wife and I had a big trip to Yellowstone National Park coming up, so I was curious about what the traffic was like to get into the park.

Conveniently, Yellowstone has a number of webcams that watch the park, including the west entrance gate, where we’d be entering.

So I thought I could leverage Simon to help me watch it over time — rather than keeping the web page open and watching it throughout the day, I can have Simon capture the webcam images to a local folder, then review at my convenience.

To find the URL of the webcam image, I used Safari’s web inspector:


Then I added a custom service to Simon to download the webcam images to a folder:

Simon service script

That uses the curl command line tool to download the image and save to a local folder; the `date -v+1H +%Y%m%d%H%M%S` part of the path outputs the date and time in the format YYMMDDHHMMSS, adding one hour from my local time zone, since Yellowstone was an hour ahead of me at the time.

To schedule the captures, I added a test in Simon that checks once per minute, using that service. No filters or notifiers needed.

That results in a folder in the Finder with files like this:


I can arrow through them to quickly view them. And I can also do other things, like use the excellent Retrobatch app to convert them to a GIF:


Click to view an example of the resulting GIF, showing the traffic flow from 06:00 to 18:00 on one day (the GIF is 61 MB, despite being scaled, so might take a moment to load); each frame of the GIF represents one minute, six frames per second:

That seems typical; it gets really busy around 06:30, and eases off around 12:30 every day. So a tip for Yellowstone visitors; enter in the afternoon! Of course, that really only works if you’re staying in the park, since it takes ages to get anywhere in the park. It’s a big place.

If you’re curious, I did several posts about this Yellowstone trip on my Sinclair Trails blog. Check it out!